1. Field of the Invention
The present invention relates to a recording paper cutting mechanism, and more particularly to a recording paper cutting mechanism capable of cutting paper into a sheet of a desired length.
2. Description of the Related Art
Printers according to the prior art having a recording paper cutting mechanism configured to be capable of cutting printed thermosensitive recording paper, for instance rolled recording paper, into a sheet of a required length, include ones at used in supermarkets and elsewhere to print receipts to be issued to customers when they have paid for their purchases.
A recording paper cutting mechanism used in such a printer may be provided with a fixed cutter (not shown) formed longer than the width of the recording paper used and a movable cutter capable of moving along this fixed cutter. The movable cutter, when not cutting paper, is in its home position and linked to a spiral shaft which can transmit the revolution of a drive motor.
The revolution of the drive motor drives the spiral shaft to shift the movable cutter along the fixed cutter and to cut the recording paper.
The thermosensitive recording paper printed by a thermal head can be fed, by the rotation of a paper feed roller toward the fixed cutter arranged farther downstream than a printing section by a desired length.
When the recording paper is to be cut, the drive motor is turned in a first direction, and this revolution is transmitted to the spiral shaft to shift the movable cutter along the fixed cutter so as to cut the recording paper into a sheet of a desired length. After the cutting is completed, the movable cutter returns to its home position.
During the process of cutting by shifting the movable cutter, the drive motor is disconnected from the paper feed roller, whose rotation is stopped so as not to feed the paper.
After the recording paper is cut and the movable cutter returns to its home position, the drive motor is turned in the reverse direction to disconnect the drive motor from the spiral shaft, and the reverse revolution of the drive motor is transmitted to the paper feed roller, which is thereby turned to feed a desired length of the printed paper toward the fixed cutter.
After that, by turning the drive motor in the first direction again, the movable cutter is shifted away from its home position and the printed paper is thereby cut into a sheet of a desired length.
Such a recording paper cutting mechanism, having advantages of simple structure and capability to cut the recording paper neatly straight, is extensively used for cutting printed receipts in, for instance, cash register machines in supermarkets and elsewhere.
However, the recording paper cutting mechanism according to the prior art involves the problem that if, during its paper cutting operation, the cutting by the movable cutter is stopped by jamming of the paper or the like, the drive motor also stops turning with the power supply to it remaining active.
This makes it necessary to reverse the spiral shaft by hand after once turning off the power supply to the drive motor, return the movable cutter to its home position, feed ahead the jammed part of the recording paper by a prescribed length, and cut off the jammed part of the paper with the movable cutter.
Thus, the conventional recording paper cutting mechanism involves the operational inconvenience that, if any trouble, such as recording paper jamming, occurs while the paper is being cut, the movable cutter should be manually returned to its home position.
The present invention, attempted in view of the problem noted above, is intended to provide a conveniently operable recording paper cutting mechanism that automatically returns a movable cutter, if it is stopped by any trouble occurring while the paper is being cut, such as recording paper jamming, to its home position and allows the jammed part of paper to be cut off and removed.
A recording paper cutting mechanism as a first means to solve the problem according to the invention has a configuration comprising:
a drive motor; cutting means consisting of a fixed cutter and a movable cutter capable of moving along this fixed cutter; a rotatable spiral shaft having spiral grooves for shifting the movable cutter; a rotatable paper feed roller for feeding recording paper toward the cutting means; a swinging board capable of swinging according to the revolving direction of the drive motor; a swinging gear fitted swingably to the swinging board and capable of selectively transmitting the revolution of the drive motor to either the spiral shaft or the paper feed roller according to the swinging direction of the swinging board; and a locking member capable of restraining the swinging of the swinging board when cutting the paper by turning the spiral shaft to shift the movable cutter along the fixed cutter.
A recording paper cutting mechanism as a second means to solve the problem according to the invention has a configuration wherein:
the movable cutter is in its home position before cutting recording paper; the recording paper is cut by turning the spiral shaft by the revolution of the drive motor to shift the movable cutter away from the home position; and, after paper cutting, the return of the movable cutter to the home position releases the swinging of the swinging board from the restraint by the locking member to enable the swinging board to swing, followed by reversing the revolution of the motor which causes the swinging board to swing thereby to enable the revolution of the drive motor to be transmitted to the paper feed roller.
A recording paper cutting mechanism as a third means to solve the problem according to the invention has a configuration wherein:
a detecting member capable of detecting the return of the movable cutter to the home position is provided, and detection by this detecting member of the return of the movable cutter to the home position causes the drive motor to turn in the reverse direction.
A recording paper cutting mechanism as a fourth means to solve the problem according to the invention has a configuration wherein:
a control unit is further provided for detecting the stop of the drive motor when the shifting of the movable cutter stops while cutting the recording paper and the drive motor stops, and the control unit, if it detects that the drive motor remains stopped for a prescribed length of time or longer, reverses the revolving direction of the drive motor to reverse the rotation of the spiral shaft and thereby to return the movable cutter to the home position.
A recording paper cutting mechanism as a fifth means to solve the problem according to the invention has a configuration wherein:
the locking member consists of an elastically deformable plate member, and the return of the movable cutter to the home position causes the movable cutter to elastically deform the movable locking member to release the swinging board from the restraint.
A recording paper cutting mechanism as a sixth means to solve the problem according to the invention has a configuration wherein:
the locking member has a restraining section formed by folding, at a right angle, part of its peripheral part, and the restraining section engages an end face of the swinging board to restrain the swinging of the swinging board.
A recording paper cutting mechanism as a seventh means to solve the problem according to the invention has a configuration wherein:
the locking member has a restraint releasing section in part of the restraining section, and the operation of the restraint releasing section when the movable cutter returns to its home position disengages the swinging board.